. Chinese mechanical and horological engineering from the Song Dynasty; this diagram provides an overall general view of the inner workings and armillary sphere of Su Song's clocktower built in Kaifeng. The drawn illustration comes from Su Song's book Xin Yi Xiang Fa Yao published in the year 1092. On the right is the upper reservoir tank with the 'constant-level tank' beneath it. In the center foreground is the 'earth horizon' box in which the celestial globe was mounted. Below that are the time keeping shaft and wheels supported by a mortar-shaped end-bearing. Behind this is the main driving Stock Photo
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